What Causes Clothes to Shrink in the Laundry

We all know the old joke about the best way to prevent clothes from shrinking is to push yourself away from the dinner table. But it isn't always our eating or laundry habits that cause clothes to shrink and change sizes. How the fabric was manufactured may make shrinkage inevitable.

What Causes Clothes to Shrink?

There are three types of clothes shrinkage: felting, relaxation, and consolidation.

Felting shrinkage occurs with animal hair fibers, like wool, that have scales along the surface. When exposed to moisture and excessive heat, these scales compress and mesh together. Example: This compression shrinkage results in the shrunken sweater syndrome if the sweater is not handled correctly.

Relaxation shrinkage happens when fabric is exposed to liquids or excessive moisture. When fabric is placed in tepid water, the fibers will relax and if the fabric is absorbent (natural fibers like cotton, silk, or linen) or modified to be absorbent (synthetic performance fibers), the fibers will swell. Relaxation shrinkage is minimal, less than one percent. Example:Hand wash a silk blouse in cool water with a gentle detergent using very little agitation or wringing action. Allow the blouse to air dry flat on a well-ventilated surface out of direct sunlight or heat. The change in size will be minimal.

Consolidation shrinkage occurs when moisture, heat, and mechanical action (agitation during washing and drying) are combined. The combination of these factors causes the fibers to release the tensions created during manufacturing of the knit or woven fabric. The release of tension deforms the fabric. Example: Toss a silk blouse into the washer with a heavy duty detergent and wash with hot water on the heavy duty cycle. Toss the blouse into a clothes dryer on high heat for 30 minutes. The change in size will be dramatic with shrinkage in both length and width. The finish of the fabric will also be damaged.

Natural fabrics like cotton, wool, and linen are more prone to shrinkage due to consolidation than synthetic fibers like polyester, acrylic, and nylon. Synthetic fibers are more stable because these fabrics are heat set (which can't be done to natural fibers) during processing to stabilize the weave or knit.

The best option when selecting natural fiber garments is to select those that are labeled as "preshrunk". The fabric is exposed to consolidation shrinkage before the garment pieces are cut and sewn.

What Is Fabric Shrinkage?

Shrinkage is defined as a change in the dimensions of a fabric or garment. The change may be negative (losing size from original measurements) or positive (growth in measurement) in the length, width, or thickness of the fabric or garment. While the thickness of a fabric can change over the course of the life of a garment, it does not usually cause a problem with the fit of a garment.

The dimensional change of fabric or a garment is caused by a force, energy, or change in environment that causes the fabric to relax or forces it to move in a given direction.

Shrinkage, whether a loss or addition of length or width dimensions, does affect the fit of a garment. Shrinkage also can account for seam puckering, torquing (pull or hang of fabric), and decorative stitching distortion.

The amount that clothes stretch or shrink depends upon the fabric's fiber content, the type of weave used, and the construction methods of the garment at the factory. Commercial fabric is made of materials that are woven or knitted together by a machine. How fibers are chosen and the weave selected determine the characteristics of the fabric. Denim jeans and t-shirts are both made from cotton fibers. The distinctive look and heaviness of denim come from the twill weave. T-shirts are made from knitted fibers that give a lighter, softer fabric.

Woven fabrics are much more stable to shrinkage factors than knitted fabrics and do not react as severely to stresses. However, they can still shrink. The amount is dependent upon how much the fabric is stretched during manufacturing if the fabric was preshrunk before garments were made, and what type of finishes were applied.

How to Manage Shrinkage During Laundry

Now you understand why clothes shrink and stretch. Many of the factors that determine whether a garment will retain its shape are established long before you get the shirt, dress, or jeans home. However, you can help control consolidation shrinkage by following care labels on clothes and using proper laundry techniques.